Back to Basics Oil Pumps

By Larry Carley

Every engine requires a certain amount of oil flow to keep the bearings, camshaft, valvetrain and other moving parts lubricated. Oil forms a barrier that prevents metal-to-metal contact and reduces friction and wear. In the bearings, it forms a wedge that actually lifts and supports the crankshaft and camshaft as they rotate.

Oil also serves as the primary means of cooling the bearings as well as the pistons. What’s more, oil also serves as a hydraulic fluid inside hydraulic lifters and lash adjusters to maintain proper valve lash. And, on some late model engines with variable valve timing, oil also moves the adjuster mechanism that advances and retards cam timing.

With so many important jobs to do, it’s obvious that the engine needs a good oil pump to deliver a steady supply of oil. But how do we know if the bearings and other moving parts are getting enough oil? Since there’s no simple way of measuring oil flow inside an engine, we look at oil pressure as a means of gauging oil flow and lubrication.

Oddly enough, an oil pump doesn’t create oil pressure. All the pump does is displace oil and push it into the oil galleys so it can flow to the bearings and upper valvetrain. What actually creates the oil pressure is the resistance the oil encounters as it circulates through the engine.

Types of oil pumps There are three basic types of oil pumps:

• Twin gear pumps, also called "external" pumps, use a pair of intermeshing gears to pump oil. One gear is driven by a shaft, and the second gear is driven by the first gear. The pump is usually driven by a shaft that connects to the crankshaft, camshaft or distributor shaft. Thus, the pump operates at half engine rpm. The pump gears turn in opposite directions. This traps oil between the gear teeth and carries it around the outside of each gear from the pickup tube inlet to the pump outlet. The tight clearances between the gears prevents the oil from flowing backwards to the inlet.

• Rotor pumps, also called "gerotor" pumps, have an inner gear that turns inside an outer rotor. The inner gear has one less lobe than the outer rotor.

The inner gear is also mounted slightly off-center to the outer rotor which forces the outer rotor to spin at about 80 percent of the speed of the inner gear.

This creates a bellows-like pumping action that pulls oil from the inlet port and pushes it toward the outlet port. Close tolerances are required for good pumping efficiency. This type of pump may also be located in the crankcase.

• Front cover pumps, also called "internal/external pumps" are usually located in the front engine cover. This is also a rotor style pump with an inner drive gear and outer rotor, but the inner gear is mounted directly on the crankshaft. The direct drive approach eliminates the need for a separate pump drive shaft.

This type of pump turns at the same rpm as the engine, so it generates more pressure at idle and does a ...

Looking for Replacement Camshaft in Mishawaka? We have compiled a list of businesses and services around Mishawaka that should help you with your search. We hope this page helps you find Replacement Camshaft in Mishawaka.